The chief investigator of the U.S. space shuttle Columbia disaster has criticized shuttle managers for underestimating the danger posed by possible left wing damage while it was still in flight. The investigating panel and members of Congress are urging changes in the shuttle bureaucracy.

The retired admiral who chairs the independent Columbia probe, Harold Gehman, told a Senate committee the U.S. space agency NASA's safety procedures failed when shuttle managers first learned Columbia's left wing might have been damaged during launch.

The investigators are looking into the possibility that pieces of hard insulating foam that broke away from the shuttle's external fuel tank during launch cracked the wing and caused Columbia's disintegration in the stress of re-entry.

Admiral Gehman said shuttle managers missed obvious signals when they rejected requests by NASA engineers for U.S. satellite images to try to learn whether the foam had damaged the wing. NASA had a prior agreement with the government's satellite imaging agency to obtain such photographs whenever it needed them, but chose not to take advantage of it in this case.

"The system didn't work, and I wouldn't blame that on any one person," he said. "We were a little disappointed in what some of the senior people knew and understood about how you get these images and what the images can do for you."

Admiral Gehman blames the failure to pay heed to engineers' worries to the fact that they are not independent from shuttle managers.

NASA administrator Sean O'Keefe told the Senate hearing that the rejection of satellite photographs is infuriating in hindsight. But he recalled that shuttle managers at the time did not consider the foam strike a risk to Columbia's safety.

"It was a judgment call," he said. "It was clearly the wrong judgment. We know now there are a variety of signals that could have told us what we should have been observing and what we could have corrected."

Shuttle managers said after the disaster that nothing could have been done to repair Columbia in orbit even if satellite imagery had revealed wing damage. But Admiral Gehman told the senators he rejects that notion. He said his investigation panel heard from engineers and former astronauts who suggested maneuvers, including spacewalks and a visit by another shuttle. The admiral points out that his board and NASA have begun a joint inquiry into possible steps that might have been taken to repair Columbia in flight.

"Even if we had a fix that had only a 10 percent chance of succeeding, of course we would have done something, absolutely," he stressed. "Thus far, this review hasn't found any magic formula, but has found several steps that could have been done to mitigate this. We may find more."

Admiral Gehman pointed out that a large portion of his panel's final report on the Columbia disaster will include recommendations for solving NASA's management problems.

Senator Olympia Snow of Washington state said NASA must change its shuttle chain of command.

"There's no question that the whole decision making process and the bureaucratic structure has to be significantly altered," she concluded.